This invention relates generally to a method for reducing the risk of illness or bodily injury arising from exposure to radiation during diagnostic procedures.
It is a well established medical fact that ionizing radiation such as emitted from X-ray equipment is capable of causing injury to both soft and hard body tissues. Principal damaging effects are usually observed as superficial injuries to the skin, general adverse effects to the body, particularly to the blood-forming organs, induction of tumors, miscellaneous effects such as cataracts, impaired fertility and adverse genetic effects. It has also been observed that tumor-inducing dosages of X-radiation will vary among persons who are exposed, typically, to low radiation doses. Hence, the minimum dose of radiation that causes tumors has not been established, notwithstanding that permissible levels of exposure are generally known which constitute an acceptable risk factor. In "Medical and Dental X-Rays", by P. W. Laws, (Health Research Group, Washington, 1974), it is pointed out that exposure to any amount of radiation is potentially harmful, yet it is possible for patients receiving a full series of diagnostic abdominal X-rays in a given year to exceed the annual occupational limit for radiation dose. Appendix D of this book compares the average doses for typical diagnostic X-ray examinations with the estimated annual excess deaths per million examinations. It is estimated that there are 30-100 excess deaths per million examinations for upper GI, 25-80 for lower GI, 5-20 for mammography, 2-7 for skull, 2-6 for dental (whole mouth) and 2-6 for chest (fluoroscopic examination). The numbers quoted above are in proportion to the estimated whole body equivalent does to which the patient is subjected. P. W. Laws concludes that if the radiation exposure can be reduced in these diagnostic procedures, it follows that the cancer risk is likewise reduced.
It has now been discovered that by underexposing a light sensitive radiograph, such as an X-ray film, to reduced levels of radiation, such that the processed film provides inadequate detail for diagnostic purposes, the image of the underexposed film can be subsequently enhanced to an image density profile equivalent to a fully exposed radiograph. A fully exposed radiograph for purposes of this invention is one in which the image detail is sufficiently distinct to the qualified observer. Radiographic image enhancement is accomplished by treating the developed and fixed film with a single-step copper ion image enhancement composition. Thus, the present invention provides a desirable means for reducing the previously accepted dosages of radiation exposure by up to 50%, and more.
Earlier efforts towards image enhancement of underexposed radiographs have not been entirely satisfactory. Chemical toners/intensifiers have been used heretofore; however, because their use required a multiplicity of processing steps they have not received wide acceptance. In addition, their highly corrosive properties and lack of stability have led to the use of additives, which in many instances were toxic substances. Furthermore, their high cost made the toning compositions economically unattractive. Still other earlier methods required the use of specially treated films, screens and apparatus, including viewing filters in order to achieve the desired image density. For example, U.S. Pat. No. 3,753,714 requires a fluorescent intensifying screen on one side of the light sensitive film. In addition, U.S. '714 generally recommends a multiple bath intensifying treatment wherein the image is blackened with a reducing substance in the second bath.
U.S. Pat. No. 2,699,994 to Umberger discloses a blue-colored iron toning bath whereby underexposed X-ray film is treated for image enhancement. Because of corrosive properties and stability problems associated with this toning formulation, additives of alpha-ether carboxylic acid e.g. diglycolic acid are required. However, it has been discovered that alpha-ether carboxylic acid compounds when used in place of more conventional sequestering agents e.g. . . . sodium citrate etc., are incompatible with copper salts in solution with ferricyanide ions causing the formation of an unacceptable precipitate. Umberger subsequently reported in the July, 1955 issue of X-Ray Technician page 19 et. seq., that toning intensification may be a means for reducing radiation to patients, but the author states that the blue toner of his U.S. Pat. No. 2,699,994 results in some increase in graininess in the intensified radiographs.
Another intensifier, Kodak Intensifier In-6, consists of three stock solutions that may be kept for several months. However, when mixed the intensifier is stable for only 2 to 3 hours and can be used only one time. Hence the brief shelf life of the prepared composition obviates repeated use of the solution.
U.S. Pat. No. 2,662,014 discloses yet another method of increasing image intensity through the use of chemical toners. However, additional processing steps are required whereby toning is preceded with a bleaching bath subsequent to developing and fixing.
Thus, according to the present invention underexposed radiographs made from radiation levels below those normally regarded as permissible and safe for diagnostic procedures for both hard and soft tissues, can be treated with a single bath, copper ion image enhancement composition to increase image density profile to a level at least equivalent to a fully exposed radiograph. The mixed copper ion image enhancement composition per se remains stable over many months, requiring no additional chemical additives or special stabilizers, can be used repeatedly without markedly exhausting the effectiveness of the bath composition, and requires no modification to either radiographic equipment or film.
In addition, the present invention has the added benefit of permitting recovery of the original silver image by simply treating the enhanced film in ordinary developing solutions, thus allowing personnel to verify the absence of false or other undesirable information. The original image can, once again, be re-enhanced in the single solution copper ion bath to obtain the enhanced image intensified by up to 50% and more.
Accordingly, it is a principal object of the present invention to provide a method for reducing patient and personnel risks arising from exposure to harmful radiation during diagnostic procedures.
It is a further object to provide a method for enhancing underexposed radiographs by means of a single step, copper ion enhancement composition to achieve an image quality at least equivalent to a fully exposed radiograph.
A still related object of the instant invention is to provide an enhancement bath for intensifying underexposed radiographs which will remain stable for prolonged time periods and can be used repeatedly.
Yet still another object of the present invention is to provide a method for enhancing the image density profile of underexposed radiographs following which the original underexposed radiograph may be recovered by redevelopment.
These and other objects, features and advantages of this invention will become apparent to those skilled in the art after a reading of the following more detailed description.